An aircraft fuel system includes a fuel line which terminates in an exposed fueling adapter at the fuel input point. Refueling facilities include a stationary or mobile fuel supply having an extended large diameter hose or articulated pipe and various pumps for delivery of the fuel under pressure. A pressure fuel servicing nozzle is secured to the delivery end of the fuel hose or pipe and is mechanically configured to engage and receive the fueling adapter. The fuel servicing nozzle is required to perform several basic mechanical functions which include mechanically engaging and locking with the fueling adapter, providing a high pressure fuel seal between the fuel delivery hose and the aircraft fuel system, and properly valving the fuel flow between the fuel system and the aircraft to provide open flow and closed seal conditions to facilitate fueling and the termination of fueling. In addition to these basic functions, modem fuel servicing nozzles provide various safety mechanisms directed toward the prevention of fuel spillage and leakage. This is critical to the operation of such refueling systems due to the highly volatile and flammable character of aircraft fuels. One such safety mechanism provides an interlock within the fuel service nozzle which prevents opening a flow control poppet valve until the nozzle has completed proper mechanical and sealing engagement with the fueling adapter.
Generally, existing fuel servicing nozzles comprise a rotating sleeve rotatably mounted upon a nozzle body which receives and locks to the aircraft fueling adapter to provide engagement. An interlock prevents the opening of the flow control poppet valve within the nozzle body until mechanical engagement as evidenced by the rotational position of the sleeve is obtained. A receiving portion within the nozzle body receives and engages the aircraft fueling adapter and includes a plurality of spring supported depressible lock pins. The lock pins prevent the rotation of sleeve in the absence of the insertion of the aircraft fueling adapter.
To connect the fuel nozzle to the fueling adapter, an operator aligns three cylindrical-shaped locating pins with three square indexing slots of the fueling adapter. When the fuel nozzle is aligned, the fuel nozzle can be pushed into the fueling adapter, thereby depressing the interlock pins which, in turn, allows the sleeve to be rotated about the nozzle body. The flow control poppet valve is now free to be opened. Of particular note is that current fuel nozzles utilize cylindrical-shaped locating pins which wear the flat surface of the indexing notches into oval-shaped notches. This effects the safety of the connection between the fuel nozzle and the fueling adapter because the nozzle body may no longer be held in the correct position when the sleeve is being rotated about the nozzle body during both connection and disconnection. Under these conditions, the fuel nozzle might be removed from a worn fueling adapter with the interlock feature defeated, allowing the flow control valve poppet to be opened when not properly connected to the fueling adapter, resulting in a dangerous spill of fuel.
Another problem which arises in existing fuel servicing nozzles is the premature wear of the mechanism which closes and opens the flow control poppet valve. Most existing fuel servicing nozzles utilize a crank shaft mechanism to open and close the flow control poppet valve. The crank shaft is positioned perpendicularly to the longitudinal axis of the nozzle body and is connected to a valve operating handle. The crank shaft includes an off-set crank arm which is connected to the poppet valve by a valve stem. As the valve operating handle is rotated to the open position, the crank shaft rotates and the crank arm is rotated and pushes the valve stem and poppet valve downward to the open position. The poppet valve is closed by rotating the operating handle back to the original position. When the fuel is pressurized by a fuel pump, large loads are imposed on the poppet valve when it is in the closed position. The load on the poppet valve is primarily supported by the crank shaft, which retains the poppet valve in the closed position. In existing fuel servicing nozzles, the crank shaft is often insufficiently supported by the nozzle body, resulting in premature wear or in extreme circumstances, fatigue failure of the crank shaft or the support structure thereof. Such premature wear or fatigue failure may lead to a leaky fuel nozzle or complete failure of the fuel nozzle to retain the fuel.
Additional problems arise due to the operating environment in which the typical fuel nozzle is utilized. The environment involves handling long relatively heavy fueling hoses under a variety of situational urgencies as well as all weather conditions. As a result, such aircraft fueling nozzles are often subjected to excessive mechanical forces. For example, the fuel servicing nozzle is often dropped or dragged on the ground, resulting in wear and damage of various unprotected components such as the valve operating handle. In addition, the portion of the nozzle body which engages with the aircraft fueling adapter may wear due to repeated connection/disconnection with the fueling adapter. Materials having high wear resistance may be used to form the nozzle body, but utilizing these high wearing materials may increase the weight of the fuel servicing nozzle to the point where it is difficult to handle.
Thus, there remains a need for an improved aircraft fuel servicing nozzle designed to connect and disconnect to a standardized fueling adapter mounted on an airframe and connected to an internal fuel manifold and tank system. In particular, a reliable and rugged fuel servicing nozzle is desireable which is light weight and easy to operate .